Saturday, August 19, 2006

understanding the internet

The internet has a packet switched architecture. Data is broken up into small packets, which are addressed and sent through the network. The same connection can be used by many users. This contrasts with circuit switching, such as the regular voice telephone network, in which the communication circuit (path) for the call is set up and dedicated to the participants in that call (and is unavailable to other users). Reference

The internet has protocols (TCP/IP) - rules encoded in software that enable communication between different types of computers (PCs, Macs) and to manage the delivery of the packets to their destination .

TCP/IP was invented by Vint Cerf and Bob Kahn:

IP which provided only for addressing and forwarding of individual packets

TCP, which was concerned with service features such as flow control and recovery from lost packets

The internet provides many services such as email, ftp, www, P2P, chat, IM, Telnet, Gopher (see diagram). Anyone with enough skill can create these services which then benefit all internet users. No one has to ask permission from anyone to create a new internet service. This is one underlying reason for the popularity of the internet.

When, seventeen years ago, I designed the Web, I did not have to ask anyone's permission. ( I did have to ask for port 80 for HTTP). The new application rolled out over the existing Internet without modifying it. I tried then, and many people still work very hard still, to make the Web technology, in turn, a universal, neutral, platform. It must not discriminate against particular hardware, software, underlying network, language, culture, disability, or against particular types of data.

I think I will use the roads metaphor in explaining the internet to my students.

I summarised one of David Weinberger's metaphors for the www as follows:

Imagine a place with billions of rooms with magic doors that are psychically linked to other rooms by the interests of the people travelling from room to room. Your nearness to other rooms is created by your level of interest. Is that magic or is that the Web?

Internet literacy:The netforbeginners site has a series of tutorials on basic internet literacy. I'm interested in pursuing this further from the point of view of the aims of Paul Chandler's wiki about conceptual understandings of computing and also also for instructing new arrivals in internet basics.

Historical / Footnotes:The internet was invented by the US military arising from their fear of a Soviet nuclear first strike.

Paul Baran, of the RAND Corporation (a government agency), was commissioned by the U.S. Air Force to do a study on how it could maintain its command and control over its missiles and bombers, after a nuclear attack. This was to be a military research network that could survive a nuclear strike, decentralized so that if any locations (cities) in the U.S. were attacked, the military could still have control of nuclear arms for a counter-attack.

Baran's finished document described several ways to accomplish this. His final proposal was a packet switched network.

"Packet switching is the breaking down of data into datagrams or packets that are labeled to indicate the origin and the destination of the information and the forwarding of these packets from one computer to another computer until the information arrives at its final destination computer. This was crucial to the realization of a computer network. If packets are lost at any given point, the message can be resent by the originator."